|M.Sc Student||Kolik Shmuel Lubov|
|Subject||Sol-Gel Thin Films Doped with Organic Molecules as a Tool|
to Study Prevention of Bacterial Adhesion Onto
|Department||Department of Civil and Environmental Engineering||Supervisor||Professor Robert Armon|
|Full Thesis text|
Bacterial cells are able to reversible attach and irreversible adhere onto almost any surface in aqueous environment, to reproduce and generate EPS as a supportive structure of a biofilm. Surfaces with the potential to prevent cellular aggregation and biofilm formation would be extremely useful in environmental, biotechnological, medical and industrial applications.
Albumin adsorbed on material surfaces has shown obvious inhibitory effects on bacterial adhesion to polymer, ceramic and metal surfaces. Tannic acid, a polyphenol, was found to be inhibitory to the growth of many bacterial strains. Tannins have the ability to form reversible or irreversible stable complexes with proteins which usually are insoluble and precipitate out of an aqueous solution. The aim of this work was to evaluate the characteristics and antibacterial properties of sol-gel entrapped coatings containing: BSA, Tannic acid and BSA - tannic acid complexes. For this purpose, we entrapped the organic substances in a 50% TEOS- 50% MTMS sol-gel matrix and applied it onto microscope glass slides. The hypothesis of the study suggests that a combination of substances natural qualities may be used for the generation of coatings with unique characteristics and improved antimicrobial properties. Two Gram (-) model bacterial strains, Escherichia coli CN13 and Pseudomonas aeruginosa HOB1 were used in the study.
Confocal scanning laser microscopy (CSLM) of stained slides demonstrated the entrapment of immobilized substances and allowed a visualization of entrapped molecules. Scanning electron microscopy (SEM) was used for the characterization of surface morphology (along with contact angle hysteresis) which is known to play a role in bacterial attachment towards different surfaces. Fourier transform infrared spectroscopy (FTIR) was utilized for chemical composition verification. Contact angle measurements were performed to determine the hydrophobic/ hydrophilic properties of the coatings surface, along with the determination of bacterial cell surface hydrophilic character.
The study showed that the adhesion of P. aeruginosa and E.coli varies with bacterial species, incubation periods, the molecular composition and the nature and concentration of entrapped molecules. Quantification of the percentage of bacterial cells attached to coated surfaces was performed using image analysis. Results demonstrated the antimicrobial effect of entrapped coatings, as all the organic substances decreased the amount of adhered bacteria after a 48 hr incubation period.